In an image forming apparatus such as a laser printer, it is known that a developing cartridge holding a developing roller is mounted to a drum cartridge holding a photosensitive drum, and these cartridges are then integrally mounted, as a process cartridge, to a main body of the apparatus.
In an example of the process cartridge, the drum cartridge has a developing cartridge housing part. The photosensitive drum is arranged at one side of the developing cartridge housing part and faces the developing cartridge housing part. In the meantime, the developing roller is provided to one end portion of the developing cartridge so that a part of a circumferential surface thereof is exposed to an outside.
When mounting the developing cartridge to the drum cartridge, the developing cartridge is arranged above the developing cartridge housing part so that the developing roller contacts the photosensitive drum. As the other end portion opposite to the side of the developing cartridge to which the developing roller is provided is pressed downwardly (toward the developing cartridge housing part), the developing cartridge is housed in the developing cartridge housing part, so that the mounting of the developing cartridge to the drum cartridge is completed. When detaching the developing cartridge from the drum cartridge, the other end portion of the developing cartridge is lifted up, so that the developing cartridge is pulled out from the developing cartridge housing part.
In order to prevent the developing cartridge from being unintentionally detached, from the drum cartridge, a lock lever having a contact piece is swingably provided to the developing cartridge housing part. When the developing cartridge is housed in the developing cartridge housing part, the contact piece of the lock lever is opposed to a predetermined part of the developing cartridge from an upper side. Accordingly, when the other end portion of the developing cartridge is lifted up, the predetermined part of the developing cartridge contacts the contact piece of the lock lever, so that a further lifting up is restrained. Thus, under such a state, it is not possible to pull out the developing cartridge from the developing cartridge housing part. When the lock lever is swung to release the contact piece of the lock lever from the upper side of the predetermined part of the developing cartridge, the lifting up of the other end portion of the developing cartridge is not restrained. Thus, it is possible to pull out the developing cartridge from the developing cartridge housing part and to thus detach the developing cartridge from the drum cartridge.